Discover interval

[w33ble]

Closes #3038

Adds interval selection to Discover, using the same interval logic used in the agg builder in visualize.

To add addition intervals (mostly, intervals that are not just 1), see #1784

• Display current interval (using bucket interval description)
• Click to alter interval - show select on click
• Remove select when set back to auto

[w33ble]

There is still some auto-scaling happening here, for example:

I'm not sure it this is something that will be adjust in #2991, but my guess is that it's really not something we can fix. Showing the value that's used might be helpful though.

[rashidkpc]

I think the auto scaling is OK here, Feb 6 - March 6 as an hourly chart would just be too many bars. I agree it would be extremely helpful to indicate that we are not showing raw counts at this point, but rather an adjusted "rate"

[w33ble]

@rashidkpc Would you like me to add the current interval to this PR as well then?

[rashidkpc]

Probably worth talking about, I'm not sure where it belongs exactly? Seems like it should go on the X-axis label somehow. Thoughts?

[w33ble]

Whoops, didn't see the question. I could display it on the axis, maybe as part of the label. Let me play with this a bit and see if I can come up with something that looks decent.

[w33ble]

@rashidkpc I opened #3535 as displaying the interval is becoming a little more involved, and I don't think it should block merging this feature. Sending back to you for review.

[w33ble]

Found an issue - when you save the search, you lose the interval state. Need to fix that.

[w33ble]

The issue right now is that the interval is only saved in the app state, which means when you save a vis, you lose the interval (since it's reloaded, and the app state is discarded).

I'm leaving this somewhat broken right now, with plans to fix it via #2716 by making that solution handle arbitrary persisted states, not limited to just visualizations.

[rashidkpc]

I think its ok to have the interval as transient for now. The chart is more of a navigational aid in the context so I don't see it as something essential to put on the savedSearch.

[rashidkpc]

Functionally this looks good, but style-wise it should use some tweaking. We were thinking something like this:

Then, when you click on "by hour" it changes to a select box.

[w33ble]

This is what I ended up with. I reset the display when the user changes the interval back to Auto

I'm using the bucket interval description (which dips in to #3535 territory) as it's the best label we have available. Alternately, I could add new labels tot he interval options, or perhaps change what's there. If that's more desirable, let me know.

[rashidkpc]

Accessing $parent to set the value from the view seems wrong. Maybe change this to be a function on the parent that sets the value. Eg:

    $scope.toggleInterval = function () {
      $scope.showInterval =  !$scope.showInterval;
    };

[w33ble]

That's how I started doing this, but it wasn't working for some reason, and $parent seemed to fix it. Of course, now that I do it again, it works fine. Oi.

[rashidkpc]

With that one comment this looks good. Would like another set of eyes here.

[panda01]

Besides that one comment, this LGTM!

[w33ble]

Ready for one last look